Suppose a1, a2, a3……is an A.P. and b1, b2, b3….. is a G.P. Then the Progression a1b1, a2b2, ……. is said to be an arithmetic-geometric progression (A.G.P). Hence an arithmetico-geometric progression is of the form ab, (a+d)br, (a+2d)br2, (a+3d)br3,………